A leg of lamb is all bittersweet

The story:

My sister and I always sang this song as kids, we had the video and watched it all the time. My parents both heard us sing the lyric and just laughed and laughed. They never told us the real lyrics (probably becuase they didn't know or didn't care). As an adult, singing in the car to myself, I finally just realized that it couldn't possibly be right. However, I could not figure it out by listening to it, it still sounded like "leg of lamb". I had to look it up on the internet. My sister and I laugh so hard that we cry when we talk about it.